The present invention relates to the field of security locks, and more particularly to an improved combination lock mechanism.
In this particular art it is old and well know to provide a combination lock mechanism including a dial, a rotatable spindle cooperating with said dial, a drive cam rigidly secured to the rearmost end of said spindle and a plurality of tumbler wheels surmounted upon said spindle proximate the drive cam and cooperating therewith. Gates are provided upon the drive cam and tumbler wheels such that manipulation of the dial in accordance with a predetermined numerical sequence aligns said gates and permits the accommodation therein of a spring-biased locking lever. Said locking lever is pivotally secured at one end thereof to a lock cam surmounting the spindle proximate the tumbler wheel assembly. A plurality of slots are disposed through the lock cam which slidably accommodate pins or the like secured to a multiplicity of locking bolt connective members. Thus, as the dial and spindle are rotated to align the drive cam and tumbler gates, the locking lever is urged into said gates and thereby engaged. The continued rotation of the dial and spindle causes the lock cam, by virtue of its securement to the locking lever, to rotate and displace the locking bolts from an extended position to a retracted position, thereby permitting the removal of the vault door and enabling access into the vault interior.
In order to minimize the breach of vault security, it is old in the art to provide a lock mechanism having a removable dial cooperating with the spindle. Briefly stated, this is conventionally accomplished by providing the spindle with an enlarged cross-sectional end face including a multiplicity of conformable recesses therethrough, a first recess aligned substantially along the lateral axis of the spindle and a second recess positioned proximate the periphery of said end face. Formed upon the back face of the dial are a multiplicity of extended pin members which may be conformably accommodated within the recesses, thereby enabling rotation of the spindle.
While the aforesaid manner of forming a removable dial provides for the positive engagement of the spindle by the dial, a drawback associated with such a configuration resides in the fact that said first recess provides a convenient guide for an individual intent upon breaching the security of the vault with a drill or punch. Once able to gain access through the spindle into the interior of the door and vault, it is a simple matter to punch off the combination lock mechanism from the threaded end of the spindle and manipulate the lock cam whereby to retract the lock bolts.
A still further drawback to such dials resides in the fact that the prior art devices are not provided with any means whereby to firmly retain the dial in place upon the spindle. Thus, an individual using the vault must constantly cope with the problem of having the dial fall off when the door is rotated to a vertical position.
In the prior art devices, the locking lever generally comprises an arcuate member aligned on its vertical edge and pivotally secured at one end thereof to the lock cam, the lever substantially conforming in geometry to the tumbler wheel assembly and arcing slightly in excess of 90.degree. about the periphery of said assembly. An inwardly directed nose and fence portion are formed at the opposite end of the locking lever, the nose and fence portions respectively engaging the gates provided upon the drive cam and tumbler assembly. A lock post secured to the vault door housing abuts the locking lever proximate said fence portion and restricts rotation of the locking lever absent the engagement of said lever within the gates.
A drawback associated with prior art locking lever designs resides in the fact that, once the security of the vault door interior has been breached, the locking lever may be manipulated outwardly away from the tumbler wheel assembly a distance sufficient to permit the nose and fence portions thereof to by-pass the lock post. Once by-passed, the lock post no longer inhibits lock cam rotation and the cam may be manipulated to retract the locking bolts.
Finally, the prior art has failed to teach or suggest any means whereby to prevent or inhibit the retraction of the locking bolts should the lock mechanism components be forcibly removed from their positions about the spindle.
Thus, it is an object of the present invention to provide an improved security vault door which retains a removable dial in place upon the end face of a spindle irrespective of the orientation of said door.
A still further object is to provide an improved security vault door which includes a locking lever preventing manipulation thereof whereby to by-pass the lock post.
Yet another object is to provide means for retaining said locking bolts in an extended and locked position should the lock mechanism components be forced from their positions surmounting the spindle.
The aforementioned several objects and others of the present invention will be readily appreciated from the following detailed description of the preferred embodiment taken in conjunction with the accompanying drawings.